This invention in general relates to grinding machines. In particular, the invention relates to an improved contour punch grinder for use in grinding metal punches.
Metal punches are utilized to punch apertures into sheet metal. The prior art machines for grinding a metal punch would pivot a metal blank into and away from the grinding wheel in order to shape the proper surface on the blank. A prior art grinding apparatus is shown in FIGS. 1 and 2. Prior art grinding apparatus 20 includes a cam 24 and a cam surface 26. Cam 24 was mounted upon a shaft 28 that rotated integrally with part holder 32. A motor rotates shaft 28, cam 24 and part holder 32. Shaft 28 and part holder 32 were mounted within main body 30, and part holder 32 had a part 34 to be ground mounted therein. As shown in FIG. 1, main body 30 is mounted to fixed base 36. Grinding wheel 38 and grinding wheel cover 40 are shown horizontally aligned with part 34.
As shown in FIG. 2, cam 24 will rotate against cam surface 26 which is fixed to stationary surface 42. Main body part 30 is pivotally mounted to base 36 as shown by pin 44. Main body 30 is weight-biased to pivot into the wheel and thus cam 24 is biased into surface 26. However, the cam shape will cause the cam 24 and main body 30 to pivot against this bias whenever a relatively large diameter portion of the cam is in contact with the cam surface. Cam 24 would rotate along cam surface 26 and cause main body 30 to pivot clockwise and counterclockwise about pin 44. Part holder 32 and part 34 would be moved therewith into and away from grinding wheel 38. Thus, by properly shaping cam 24, a desired surface can be formed upon contour punch part 22.
This type of prior art device was unsatisfactory since a cam needed to be manufactured for any run of contour punches that was to be manufactured. This is not particularly expensive if a large number, say thousands or hundreds of thousands, of the contour punches were to be manufactured; however, if only a small number of punches were to be manufactured it would be unduly expensive to create a cam such as shown at 24.
One prior art device attempted to solve this problem by computerizing a motor to pivot main body part 30 into and away from grinding wheel 38. This was also unsatisfactory since the computer program was extremely complicated and required the introduction of several variables.
A contour punch as is commonly found in industry is shown in FIG. 3. This punch consists of a main body portion 46 that may sometimes have a ramp portion 48 extending between main body portion 46 and a flat planar surface 50. A lock nut indentation 52 is formed near one end 54, the planar surface 50 being formed at the other end 56. In contour punch 22, surfaces 48 and 50 have been formed by a grinding wheel while main portion 46 is relatively unground and retains its original shape. When utilizing a prior art grinder that pivoted, a flat planar surface, such as shown at 50, will have wavy surfaces. The prior art grinding wheels were not capable of grinding a completely flat surface by merely pivoting into and away from the grinding wheel.
It is therefore an object of the present invention to create a grinding apparatus that will allow the use of either a cam or a computer control to control the movement of the contour punch part holder into and away from the grinding wheel.
It is further an object of the present invention to create a contour punch grinder apparatus that will grind a perfectly flat surface when one is desired upon a particular contour punch.
Moreover, it is an object of the present invention to achieve these goals with an apparatus that is relatively simple and economical.